1. Technical Field of the Invention
The present invention concerns the area of analog/digital signal conversion, and in particular the methods for sampling several analog signals with an analog/digital converter.
2. Description of Related Art
A method is known for measuring at least two analog signals, including at least one operation that consists of creating digital samples, at successive sampling instants and at least by means of a first analog/digital converter, representing the values taken respectively by these signals at these sampling instants. Such a method is well known to the professional engineer. It is employed, for example, in motor monitoring applications for three-phase motors.
The problem is to be able to measure, and convert into digital form, the simultaneous value of at least two analog signals.
To this end, certain solutions of previous design aim to use and synchronize at least two converters, with each converter measuring one signal.
However such solutions are particularly costly and are not satisfactory in terms of size at the silicon level. Moreover, in this area, it is preferable to have no more than one analog/digital converter.
Now by its nature, a single converter cannot be used to effect several measurements simultaneously. Two successive measurements of a given signal, or of two different signals, can be achieved only with a time offset between these measurements.
Moreover, the time offset between the measurements, with the use of a single converter, introduces inaccuracy into the measurements when they are considered to be simultaneous.
For example, in the context of motor monitoring applications for balanced three-phase motors, it is no longer possible to operate on the basic assumption that the sum of the three currents is zero at a given instant with a single converter, and if this assumption is nevertheless considered to be true with measurements that are offset in time, then that introduces inaccuracy into the measurements for monitoring the motor, and a potential drop in its performance.
In order to overcome these effects, there do exist certain solutions aiming to compensate, by software, for the offset between two successive measurements, but they are particularly complex to implement and require the measurement or the evaluation of other parameters.
There is a need to remedy these drawbacks by proposing a method that is particularly simple to implement, and that aims to get around the constraint according to which a single converter is unable to effect several simultaneous measurements.